Low night temperature effects on photosynthetic performance on two grapevine genotypes

The functional activities of the photosynthetic apparatus of two grapevine genotypes (Vitis vinifera L. cvs. Müller-Thurgau and Lagrein) were investigated after low night temperature (LNT) treatment for 7 d. LNT caused important reductions of the net photosynthetic rate (P_N) of Lagrein plants due to non-stomatal components. These non-stomatal effects were not evident in Müller-Thurgau. At LNT treatment, the contents of photosynthetic pigments decreased significantly in Lagrein, but in Müller-Thurgau the contents of chlorophyll (Chl) remained unchanged whereas the contents of carotenoids (Car) increased. An increase and decrease of Chl a/b was shown in Mü ller-Thurgau and Lagrein stressed plants, respectively. RuBPC activity and content of soluble proteins were also significantly reduced in Lagrein. Under LNT treatment, photosystem (PS) 2 was markedly more inhibited in Lagrein than in Müller-Thurgau. The decrease in PS 2 activity in Lagrein was mostly due to the marked loss of D1, 47, 43, 33, 28-25, 23 and 17 kDa proteins determined by immunological and SDS-PAGE studies.     

Protective Effect of Triacontanol Against Acidic Mists in Samanea saman (Jacq.) Merrill Seedlings: Differential Responses in Growth, 14CO2 Fixation,Ribulose-1,5-Bisphosphate Carboxylase,and Electron Transport Activities

Seedlings of tropical leguminous tree Samanea saman (Jacq.) Merrill were exposed for 7 d to acidic mist (AM, induced by H₂SO₄) of pH 5.6, 4.0, and 2.0. AM significantly reduced seedling growth (root and shoot length, leaf density, leaf area, fresh and dry mass accumulation) and photosynthetic activities. In thylakoids isolated from leaves treated at pH 4.0 and 2.0 a decrease in the activities of photosystem (PS) 2 and whole chain electron transport was observed, but PS1 activity did not change. When the seedlings were subsequently sprayed with triacontanol (TRIA), the AM effect was partially or completely reversed indicating that TRIA can protect from AM effects. The artificial electron donors, di-phenylcarbazide (DPC) and hydroxylamine (NH₂OH), markedly restored the loss of PS2 activity in AM (pH 2.0) treated leaves. This is the first report of alleviating the AM by TRIA in tropical tree seedlings.     

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

The grapevine (Vitis vinifera L. cv. Riesling) plants subjected to water deficit were studied for changes in relative water content (RWC), leaf dry mass, contents of chlorophyll (Chl), total leaf proteins, free amino acids, and proline, and activities of ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR), and protease. In water-stressed plants RWC, leaf dry matter, Chl content, net photosynthetic rate (P _N), and RuBPC and NR activities were significantly decreased. The total leaf protein content also declined with increase in the accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. A significant two-fold increase in proline content was recorded.     

Induction of heat shock-like proteins in Vigna sinensis seedlings growing under ultraviolet-B (280-320 nm) enhanced radiation

The effect of ultraviolet-B (UV-B) enhanced fluorescent radiation on protein profile and protein synthesis has been investigated in Vigna sinensis L. cv. Walp seedlings growing at various temperatures. In seedlings growing at 30°C, UV-B radiation decreased the level of several proteins as seen in Coomassie brilliant blue stained gel. However, fluorography of the same gel indicates induction of three sets of proteins in the range of 70. 53 and 16 k Da. Such induction under UV-B enhanced radiation resembled that found after heat shock treatments. In seedlings at 10 and 20°C, induction of such proteins varied both qualitatively and quantitatively. At 40°C. UV-B enhanced radiation caused a cumulative effect with temperature. Strong induction of specific proteins by UV-B radiation in seedlings growing under normal temperature indicates a possible protective role.     

Photosynthetic changes that occur during aging of cypress (Cupressus sempervirens L.) needles

2-years-old cypress needles (A2) were physiologically most active with regard to net photosynthetic (P _N) and electron transport rates. Variable to maximum fluorescence (F_v/F_m) ratios of dark-adapted needles were higher in A2 needles than in current year (A1) or senescent (A4) needles. Lower F_v/F_m values in these stages seemed to be caused not by photoinhibition but by a low photochemical capacity as suggested from the chlorophyll (Chl) a/b ratios. In isolated thylakoids, lower rates of whole chain and photosystem 2 (PS2) activities were observed in A4 needles, while higher rates were observed in A2 needles. A similar trend was noticed for contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC) and total soluble proteins. The artificial exogenous electron donor Mn²⁺ failed to restore the loss of PS2 activity in 3-year-old (A3) and A4 needles, while diphenylcarbazide and NH₂OH significantly restored the loss of PS2 activity. The marked loss of PS2 activity in A4 needles was primarily the result of the loss of 33, 28–25, 23, and 17 kDa polypeptides. A marked loss of RuBPC activity in A4 needles is mainly due to the loss of 15 (SSU) and 55 (LSU) kDa polypeptides.     

Effect of Cd and UV-B radiation on polypeptide composition and photosystem activities ofVigna unguiculata chloroplasts

Rates of whole chain and photosystem 2 activities in chloroplasts isolated fromVigna unguiculata L. seedlings grown under ultraviolet-B (UV-B) enhanced radiation were less affected by 3, 6 and 9 mM CdCl₂ for 60 min at 0 °C in the dark than the rates in chloroplasts from control plants grown under normal irradiation. The results are in agreement with changes in contents of chloroplast 55, 47, 43, 33, 29, 27–25, 23 and 17 kDa polypeptides that were significantly lowered at 3, 6 and 9 mM CdCl₂ only in chloroplasts from control plants. On the other hand, in the simultaneous treatment of chloroplast isolated from control plants the UV-B supported the inhibitory effect of all applied concentrations of CdCl₂. The photosystem 1 activity was only marginally affected in the all experimental variants.     

Effects of Phytoplasma Infection on Growth and Photosynthesis in Leaves of Field Grown apple (Malus Pumila Mill. cv. Golden Delicious)

The contents of chlorophyll (Chl), leaf biomass, and soluble proteins were markedly decreased in phytoplasma infected apple leaves. Similar results were also observed for ribulose-1,5-bisphosphate carboxylase, ¹⁴CO₂ fixation, and nitrate reductase activity. In contrast, the contents of sugars, starch, amino acids, and total saccharides were significantly increased in phytoplasma infected leaves. In isolated chloroplasts, phytoplasma infection caused marked inhibition of whole photosynthetic electron chain and photosystem 2 (PS2) activity. The artificial exogenous electron donor, diphenyl carbazide, significantly restored the loss of PS2 activity in infected leaves. Similar results were obtained when F_v/F_m was evaluated by in vivo Chl a fluorescence kinetic measurements.     

Changes in photosynthetic apparatus during dark incubation of detached leaves from control and ultraviolet-B treatedVigna seedlings

Changes in various components of photosynthetic apparatus during the 4 d dark incubation at 25°C of detached control and ultraviolet-B (UV-B) treatedVigna unguiculata L. leaves were examined. The photosynthetic apparatus was more degraded in younger control seedlings and for a longer time UV-B treated seedlings than in the older or for a shorter time UV-B treated seedlings. This was shown by determining the losses in chlorophyll (Chl) and protein contents, variable fluorescence yield, photosystem (PS) 2, PS1 and ribulose-1,5-bisphosphate carboxylase (RuBPC) activities, and photosynthetic¹⁴CO₂ fixation. In contrast, the Car/Chl ratio increased during the dark incubation due to less expressed degradation of Car.     

Effects of Phytoplasma [Stolbur-Subgroup (Bois Noir-BN)] on Photosynthetic Pigments,Saccharides, Ribulose 1,5-Bisphosphate Carboxylase,Nitrate and Nitrite Reductases,and Photosynthetic Activities in Field-Grown Grapevine (Vitis vinifera L. cv. Chardonnay) Leaves

In leaves of field-grown grapevine, the contents of chlorophyll, carotenoids, and soluble proteins and the activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and nitrate (NR) and nitrite (NiR) reductases were decreased in phytoplasma-infected leaves, but the contents of soluble sugars and total saccharides were markedly increased. In isolated thylakoids, phytoplasma caused marked inhibition of whole chain and photosystem 2 (PS2) activities. The artificial exogenous electron donor, diphenyl carbazide, significantly restored the loss of PS2 activity in infected leaves.